1. Field of the invention
The present invention relates to a pipe junction switch for two-cylinder thick-material pumps with a pivot pipe pivotable in front of a cylinder-side wear plate furnished with openings, where a wear ring is disposed axially shiftable to a limited amount on the cylinder-side end of the pivot pipe.
2. Brief Description of the Background of the Invention Including Prior Art
Pipe switches of this kind which carry a wear ring, which is automatically hydrostatically adjusting and which is designated as automatic ring, are known for example the German Patent DE-PS 2,614,895 and German Patent DE-PS 3,103,321. According to the references, the wear ring and/or the pivot pipe includes annular turned grooves for receiving of the rubber-elastic sealing ring. However, in practical situations, it can be hardly avoided that the material to be transported passes and penetrates into the intermediate space between the sealing ring on the one hand and the pivot pipe or, respectively, the wear ring on the other hand. This generates the danger that the sealing ring is pushed radially inwardly and out of the intermediate space between the pivot pipe and the wear ring and thereby the sealing and wear-balancing effect of the sealing ring deteriorates. Consequently, it is frequently only possible to a limited amount to transport stiff-plastic, fine-grained material such as, for example, fine mineral pastes, as they are employed and encountered in ore mining or in the mineral oil industry, with the known pipe switch pumps. If the material to be transported changes in its compositions frequently and substantially between coarse and fine grains, as occurs for example in the clearing of rivers from mud and in the transportation of overburden in mining and tunnel construction, undesired sealing problems occur for this reason again and again in the case of the use of pipe switch pumps.